A typical data storage system includes a housing that encloses a variety of components. For example in a disc drive, the components include at least one rotating disc having data on one or more surfaces that are coated with a medium for storage of digital information in a plurality of circular, concentric data tracks. The disc(s) are mounted on a spindle motor that causes the disc(s) to spin and the data surfaces of the disc(s) to pass under respective hydrodynamic bearing slider surfaces. The sliders carry transducers, which write information to and read information from the data surfaces of the disc(s). An actuator mechanism moves the sliders from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each slider. The suspension includes a load beam and a gimbal (or flexure). The load beam provides a preload force, which forces the slider toward the disc surface. The gimbal is configured to couple the head to the load beam. Therefore, the gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and/or roll while following the topography of the disc.
The preload force, provided by the load beam, applies a force on the slider at a load point. Generally, the load point is located such that the preload force is applied to the slider through a feature such as a dimple or hemispherical radius formed in the gimbal or load beam. The preload force counteracts the lifting force from the slider's hydrodynamic bearing surface. Precise control of the preload force results in a slider that will fly above the disc(s) at a desired fly height (or contact the disc surface with a desired contact force in direct-contact or pseudo-contact applications).
As disc drives continue to be improved, there is a desire to increase performance while decreasing size and manufacturing costs. As a result, the size of the suspension assembly that provides the electrical and mechanical interconnection between the slider and the actuator mechanism has also been reduced. Improving performance and reducing costs are conflicting objectives and, therefore, can be difficult to achieve.
One of the most common suspension assembly issues is the position of the slider relative to the medium. Vertical separation between slider and the data track on the medium is one type of position issue. If the slider is too far above the data track the electromagnetic interaction between the slider and the medium will be weak, resulting in poor data storage. If the slider is too close to the medium then mechanical contact between the slider and the spinning medium can become too frequent, or too severe, or both, (for non-contact applications) thereby affecting the reliability of the disc drive. Poor vertical separation between the slider and the medium can be the result of deviations of the load force applied by the load beam. Besides deviations in load force, poor vertical separation between the slider and the medium can be the result of the suspension failing to present the bearing surface of the slider in a parallel fashion to the surface of the medium. If the bearing surface of the slider is not parallel to the surface of the disk when the head is presented, then the gimbal will deflect in order to allow the slider to comply with the medium. This gimbal deflection results in moments, or torques, opposing the deflection. These moments can be developed from either pitch rotation of the gimbal, or roll rotation of the gimbal, or both.
The mechanical integrity of the suspension is another factor that can affect the positioning of slider. Specifically, shock and vibration can be the most serious. Small sized disc drives that are mounted in portable consumer devices (e.g., notebook computers and portable music players and other types of devices) are especially susceptible to shock and vibration. It is fairly easy to accidentally drop a disc drive or the system in which it is mounted. Such accidental drops can cause significant shock pulses to pass through the various components within the disc drive and can cause the slider to lift away from the medium, and then crash back against the medium causing severe damage to the medium, head, or both. Furthermore, during the lifting period of the shock event, the slider can sometimes separate away from suspension. Such separation can deform and damage the gimbal.
A need exists for an improved design of suspension assemblies for sliders that ensures sufficient load point contact force and control of pitch and roll static angles independent of the load point contact force.
Embodiments of the present invention provide solutions to these and/or other problems and offer other advantages over the prior art.